Find the chance when rolling 3 dices the the reminder of divid the sum by 4.

ThreeDiceMod4Chance.swift

import Foundation

func diceChance() {
    var sums = [Int: Int]()
    for i in 1...6 {
        for j in 1...6 {
            for k in 1...6 {
                sums[i+j+k, default: 0] += 1
            }
        }
    }
    print(sums.sorted{a,b in
        a.key < b.key
    })
    
    let dealer = sums.reduce(into: [:]) { modFour, element in
        modFour[element.key % 4, default: 0] += element.value
    }
    
    print(dealer.sorted{a,b in
        a.key < b.key
    })
}

diceChance()

output:

[(key: 3, value: 1), (key: 4, value: 3), (key: 5, value: 6), (key: 6, value: 10), (key: 7, value: 15), (key: 8, value: 21), (key: 9, value: 25), (key: 10, value: 27), (key: 11, value: 27), (key: 12, value: 25), (key: 13, value: 21), (key: 14, value: 15), (key: 15, value: 10), (key: 16, value: 6), (key: 17, value: 3), (key: 18, value: 1)]
[(key: 0, value: 55), (key: 1, value: 55), (key: 2, value: 53), (key: 3, value: 53)]